What Are Hard Wired Smoke Detectors?

Hardwired Smoke Detectors

• Traditional smoke detectors have generally been standalone, battery-powered units. A 9-volt or similar battery provides the electrical power for the detector. These units required frequent testing, annual battery replacement and, in the event of a battery failure, would not operate. Hardwired smoke detectors are a common feature in many new and remodeled American homes. These units use household voltage to operate and can be wired together so that, if one detector is triggered, all other alarms in the home will sound simultaneously. Hardwired units generally use a battery to provide backup power in the event of a power outage. Since they use household voltage, hardwired smoke detectors provide a better array of additional features like emergency lighting and strobes for people with hearing problems.

Ionization Smoke Detectors

• Ionizing smoke detectors use a very small amount of radioactive material to create an electrical charge that is monitored by the detector. As smoke enters the detector, the smoke particles interfere with the electrical charge and the change in voltage triggers an alarm. The smoke detector will then sound an alarm until it is silenced or all smoke clears the sensor area.

Photoelectric Smoke Detectors

• Photoelectric smoke detectors rely on a light source and photoelectric cell to detect the presence of smoke. The light source is directed away from the photo cell, resulting in no light being detected. As smoke enters the detector, light is reflected off the smoke particles, causing some of the light to fall on the photoelectric cell. When the detector senses the presence of light on the photo cell, it triggers the alarm. Like the ionizing detector, the alarm will sound until silenced or until the smoke is cleared.

Dual Technology Smoke Detectors

• As the name implies, dual sensor smoke detectors employ both ionizing and photoelectric technologies. Each sensor is better suited for different types of fires. Hot, flaming fires are more likely to quickly trigger ionizing detectors while photoelectric detectors are more suited for smoky, smoldering fires. Since predicting the type of fire homeowner's may experience is impossible, the United States Fire Agency recommends using either a mixture of both types of sensors or dual technology detectors.